Graphite Radio Battery Core

These small, grey, matte, cylindrical rods are made from graphite, a form of carbon. They are brittle – you can see the smooth, brittle fracture surface where they have snapped apart. These particular rods were found inside a Roberts radio from the 1960s. It is likely that they formed part of a dry zinc-carbon battery, a common battery in low-power devices such as a radios, clocks or handheld electric torches. In fact, dry batteries were what made early portable electronics possible; unlike the earlier ‘wet cells’ which contained liquid electrolytes, dry batteries use electrolyte pastes, so can be used in any orientation without leakage.

Graphite is a naturally-occurring mineral, and its special atomic structure has made it incredibly technologically useful. In graphite, carbon atoms are bonded together in single atom thick layers. These bonds are incredibly strong, but the layers are stacked one on top of the other like the pages of a book, and the bonds between these layers are very weak. This makes graphite a good solid lubricant, because the layers can easily slip and slide over one another. It is also why graphite is found in pencils – the friction between the pencil tip and paper is enough to break the weak bonds and rub layers off onto the page. In addition, electrons can flow between layers, which allows graphite to conduct electricity, an unusual property for a non-metal. For this reason, and its low reactivity, graphite is often used in industry as electrodes in steelmaking and in batteries, like these graphite rods.